Apparatus and method for providing handover support information in mobile communication system

ABSTRACT

An apparatus and method for providing handover support information in a mobile communication system are provided. A method for an Base Station (BS) to provide information necessary for measurement report trigger performance to a Mobile Station (MS) after the MS determines neighboring BSs in a mobile communication system includes, in a case where the MS is an active mode MS, providing a Time To Trigger (TTT) independently by a specific neighboring BS to the active mode MS and, in a case where the MS is an idle mode MS, providing a reselection time period (Treselection) independently by the specific neighboring BS to the idle mode MS.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application is a continuation application of prior application Ser.No. 16/787,553 filed on Feb. 11, 2020; which is a continuationapplication of prior application Ser. No. 15/007,662 filed on Jan. 27,2016, which has issued as U.S. Pat. No. 10,602,420 on Mar. 24, 2020;which is a continuation of prior application Ser. No. 14/107,616 filedon Dec. 16, 2013, which has issued as U.S. Pat. No. 9,247,464 on Jan.26, 2016; and which is a continuation application of prior applicationSer. No. 13/095,238 filed on Apr. 27, 2011, which has issued as U.S.Pat. No. 8,611,904 on Dec. 17, 2013 and claimed the benefit under 35U.S.C. § 119(a) of a Korean patent application filed on Apr. 27, 2010 inthe Korean Intellectual Property Office and assigned Ser. No.10-2010-0038886, the entire disclosure of each of which is herebyincorporated by reference.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention relates to an apparatus and method for providing aTime To Trigger (TTT) for handover of a User Equipment (UE). Moreparticularly, the present invention relates to an apparatus and methodfor providing a Time To Trigger for handover of a User Equipment and atime period (Treselection) for cell reselection of the UE in a mobilecommunication system.

2. Description of the Related Art

Recently, a demand for high-speed data services has been continuouslyincreasing in mobile communication systems. The data services areprovided mainly in a specific small area at the coverage side, soattention is increasingly being paid to a micro cell (or a pico cell, ahot zone, a femto cell, and the like).

The characteristics of a micro cell are given as follows. The micro cellhas a smaller coverage than a macro cell, and may overlap with the macrocell. Also, the micro cell can operate in the same or differentfrequency from the macro cell, and makes use of a low transmit powercompared to a macro evolved Node B (eNB).

However, in a case where a UE performs handover from a macro cell to amicro cell, there is a problem that the use of an existing setting valuefor handover as used between macro cells results in high handoverfailure probability.

Therefore, a need exists for an apparatus and method for providinghandover support information in a mobile communication system.

SUMMARY OF THE INVENTION

Aspects of the present invention are to address at least theabove-mentioned problems and/or disadvantages and to provide at leastthe advantages below. Accordingly, an aspect of the present invention isto provide an apparatus and method for providing HandOver (HO) supportinformation in a mobile communication system.

Another aspect of the present invention is to provide an apparatus andmethod for providing a Time To Trigger (TTT) for handover of a MobileStation (MS) in a mobile communication system.

A further aspect of the present invention is to provide an apparatus andmethod for providing a time period (Treselection) for cell reselectionof a MS in a mobile communication system.

Yet another aspect of the present invention is to provide an apparatusand method for, in order to support a stable handover success athandover performance between macro and micro cells, negotiating TTTrelated information between Base Stations (BSs) in a 3rd GenerationPartnership Project Long Term Evolution (3GPP LTE) based system.

Still another aspect of the present invention is to provide an apparatusand method for a serving BS to forward a TTT value independently by aspecific neighboring BS to an active mode MS for the sake of stablehandover performance between macro and micro cells in a 3GPP LTE system.

Still another aspect of the present invention is to provide an apparatusand method for a serving BS to forward a Treselection valueindependently by a specific neighboring BS to an idle mode MS for thesake of stable cell reselection performance between macro and microcells in a 3GPP LTE system.

The above aspects are achieved by providing an apparatus and method forproviding handover support information in a mobile communication system.

According to an aspect of the present invention, a method for an BS toprovide information necessary for measurement report trigger performanceto a MS, after the MS measures neighboring BSs in a mobile communicationsystem, is provided. The method includes, in a case where the MS is anactive mode MS, providing a TTT independently by specific neighboring BSto the active mode MS and, in a case where the MS is an idle mode MS,providing a reselection time period Treselection independently by aspecific neighboring BS to the idle mode MS.

According to another aspect of the present invention, a method for an BSto transmit handover information of a MS to another BS in a mobilecommunication system is provided. The method includes performingnegotiation by sending a mobility change message including mobilitychange information to a neighboring BS, and receiving a response messageto the mobility change message.

According to a further aspect of the present invention, a method foracquiring mobility information of a neighboring BS in a MS of a mobilecommunication system is provided. The method includes, in a case wherethe MS is in an active mode, receiving the mobility information of theBS through a control message, determining if a measurement reportcondition is met, based on the mobility information included in thecontrol message, in a case where the measurement report condition ismet, transmitting a measurement report message to the BS, in a casewhere the MS is in an idle mode, receiving the mobility information ofthe BS through a System Information Block (SIB), determining if a cellreselection condition is met, based on the mobility information includedin the SIB, and, in a case where the cell reselection condition is met,performing cell reselection.

According to yet another aspect of the present invention, an apparatusof an BS providing information of a neighboring BS to a MS in a mobilecommunication system is provided. The apparatus includes a controllerand a transmitter. In a case where the MS is an active mode MS, thecontroller generates a TTT independently by a specific neighboring BS.In a case where the MS is an idle mode MS, the controller generates aTreselection independently by a specific neighboring BS. The transmittertransmits the generated TTT to the active mode MS and transmits thegenerated Treselection to the idle mode MS.

According to still another aspect of the present invention, an apparatusof an BS for transmitting handover information of a MS to another BS ina mobile communication system is provided. The apparatus includes acontroller, a transmitter, and a receiver. The controller generates amobility change message including mobility change information. Thetransmitter transmits the mobility change message to a neighboring BS.The receiver receives a response message to the mobility change message.

According to still another aspect of the present invention, an apparatusof a MS for acquiring mobility information of a neighboring BS in amobile communication system is provided. The apparatus includes acontroller and a receiver. In a case where the MS is in an active mode,the controller acquires the mobility information of the BS through acontrol message, determines if a measurement report condition is metbased on the mobility information included in the control message and,in a case where the measurement report condition is met, transmits ameasurement report message to the BS. In a case where the MS is in anidle mode, the controller acquires the mobility information of the BSthrough a SIB, determines if a cell reselection condition is met basedon the mobility information included in the SIB, and, in a case wherethe cell reselection condition is met, performs cell reselection. Thereceiver receives the control message and the SIB.

Other aspects, advantages, and salient features of the invention willbecome apparent to those skilled in the art from the following detaileddescription, which, taken in conjunction with the annexed drawings,discloses exemplary embodiments of the invention

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects, features, and advantages of certainexemplary embodiments of the present invention will become more apparentfrom the following description taken in conjunction with theaccompanying drawings in which:

FIG. 1 is a diagram illustrating an example of a heterogeneous networkaccording to an exemplary embodiment of the present invention;

FIG. 2 is a message flow illustrating a process of sending a measurementreport message according to an exemplary embodiment of the presentinvention;

FIG. 3 is a diagram illustrating a change of DownLink (DL) receivedsignal strength at handover from a macro cell to a micro cell accordingto an exemplary embodiment of the present invention;

FIG. 4 is a diagram illustrating a HandOver (HO) process dependent on aposition of a User Equipment (UE) when the UE performs handover from amacro cell to a macro cell according to an exemplary embodiment of thepresent invention;

FIG. 5 is a diagram illustrating a handover process dependent on aposition of a UE when the UE performs handover from a macro cell to amicro cell according to an exemplary embodiment of the presentinvention;

FIG. 6 is a diagram illustrating a handover process dependent on aposition of a UE when the UE performs handover from a macro cell to amicro cell according to another exemplary embodiment of the presentinvention;

FIG. 7 is a ladder diagram illustrating a mobility change process of anevolved Node B (eNB) according to an exemplary embodiment of the presentinvention;

FIG. 8 is a flowchart illustrating a mobility change process of an eNBaccording to an exemplary embodiment of the present invention;

FIG. 9 is a message flow diagram illustrating a process of forwardingTTT and Treselection values independently by a neighboring eNB to a UEin a serving eNB according to an exemplary embodiment of the presentinvention;

FIG. 10 is a flowchart illustrating a process of forwarding TTT andTreselection values independently by a neighboring eNB to a UE in aserving eNB according to an exemplary embodiment of the presentinvention;

FIG. 11 is a block diagram illustrating a construction of an eNB or a UEaccording to an exemplary embodiment of the present invention;

FIG. 12 is a graph illustrating an HO fail ratio result when a loadfactor is 50% and an UpLink (UL) Interoperability Test (IoT) is 5 dBaccording to an exemplary embodiment of the present invention; and

FIG. 13 is a graph illustrating an HO fail ratio result when the loadfactor is 100% and the UL Interoperability Test (IoT) is 7 dB accordingto an exemplary embodiment of the present invention.

Throughout the drawings, like reference numerals will be understood torefer to like parts, components and structures.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

The following description with reference to the accompanying drawings isprovided to assist in a comprehensive understanding of exemplaryembodiments of the invention as defined by the claims and theirequivalents. It includes various specific details to assist in thatunderstanding but these are to be regarded as merely exemplary.Accordingly, those of ordinary skill in the art will recognize thatvarious changes and modifications of the embodiments described hereincan be made without departing from the scope and spirit of theinvention. Also, descriptions of well-known functions and constructionsare omitted for clarity and conciseness.

The terms and words used in the following description and claims are notlimited to the bibliographical meanings, but, are merely used by theinventor to enable a clear and consistent understanding of theinvention. Accordingly, it should be apparent to those skilled in theart that the following description of exemplary embodiments of thepresent invention is provided for illustration purpose only and not forthe purpose of limiting the invention as defined by the appended claimsand their equivalents.

It is to be understood that the singular forms “a,” “an,” and “the”include plural referents unless the context clearly dictates otherwise.Thus, for example, reference to “a component surface” includes referenceto one or more of such surfaces.

By the term “substantially” it is meant that the recited characteristic,parameter, or value need not be achieved exactly, but that deviations orvariations, including for example, tolerances, measurement error,measurement accuracy limitations and other factors known to skill in theart, may occur in amounts that do not preclude the effect thecharacteristic was intended to provide.

Exemplary embodiments of the present invention provide an apparatus andmethod for providing HandOver (HO) support information in a mobilecommunication system.

The 3^(rd) Generation Partnership Project Radio Access NetworkWorkingGroup 1 (3GPP RAN WG1) is considering a heterogeneous network asa Long Term Evolution (LTE)—Advanced study item from 2009 Octoberconference. The Heterogeneous Network (HetNet) means a cellulardeployment of a form in which micro evolved Node Bs (eNBs) using lowertransmission outputs are overlaid with each other within an area of amacro eNB.

That is, in the HetNet, cells of different sizes are mixed or overlaidwith each other. Here, all eNBs use the same wireless transmissiontechnology.

FIG. 1 is a diagram illustrating an example of a heterogeneous networkaccording to an exemplary embodiment of the present invention.

Referring to FIG. 1, within an area managed by a macro eNB 100 of theheterogeneous network, there are pico cells 130 and 140 and femto cells150, 160, and 170, and there are micro cells with radio networks 110 and120 of a small scale.

In exemplary embodiments of the present invention, a description is madeconsidering a 3^(rd) Generation Partnership Project Long Term Evolution(3GPP LTE) based system.

An exemplary embodiment of the present invention relates to a methodfor, when a User Equipment (UE) performs handover between macro andmicro cells, efficiently supporting the handover at heterogeneousnetwork deployment.

More particularly, an exemplary embodiment of the present inventiondescribes a way for negotiating Time To Trigger (TTT) relatedinformation between eNBs in the 3GPP LTE based system.

Also, an exemplary embodiment of the present invention relates to amethod for an idle mode UE to efficiently support cell reselectiontriggering, when the idle mode UE performs cell reselection betweenmacro and micro cells.

An exemplary embodiment of the present invention describes a way for aserving eNB to forward TTT and reselection time period (Treselection)values independently by a neighboring eNB to a UE in the 3GPP LTE basedsystem.

An active mode UE compares two received signal strengths with each otherafter measuring Reference Signal Received Power (RSRP) of a serving eNBand a target eNB. After that, the active mode UE sends a measurementreport message to the serving eNB if a measurement trigger condition ismet.

In an LTE system, there are several kinds of measurement triggerconditions, but the most widely used measurement trigger condition(Event A3) among them is given in Formula 1 below.Entering condition:Mn+Ofn+Ocn−Hys>Ms+Ofs+Ocs+OffLeaving condition:Mn+Ofn+Ocn+Hys<Ms+Ofs+Ocs+Off  (1)

where,

Ms: RSRP (Signal to Interference+Noise Ratio (SINR)) measurement valueof a serving cell (decibel (dB));

Mn: RSRP (SINR) measurement value of a neighbor cell (dB);

Ofs: offset considering carrier frequency of the serving cell (dB);

Ofn: offset considering carrier frequency of the neighbor cell (dB);

Ocs: offset used for signal level control of the serving cell athandover performance (dB);

Ocn: offset used for signal level control of the neighbor cell athandover performance (dB); and

Off: offset for reflecting feature of Event A3 (dB).

An Event A3 takes place if a leaving condition is not met during a TTTtime after a UE meets an entering condition. Here, the TTT value means atime to meet the measurement trigger condition in order to trigger ameasurement event. The LTE system can select and apply one of sixteenTTT values according to a speed of a UE.

The ‘Ocn’ value, which is an offset value added to or subtracted from aneighboring cell signal level at handover performance, can bedifferently set every specific two cells. The ‘Ocs’ value, which is anoffset value added or subtracted from a serving cell signal level athandover performance, is a parameter existing every specific cell.

If receiving a measurement report from a UE, a serving eNB determineshandover or non-handover of the UE with reference to Radio ResourceManagement (RRM) information.

FIG. 2 is a message flow illustrating a process of sending a measurementreport message according to an exemplary embodiment of the presentinvention.

Referring to FIG. 2, in an LTE system, there are several kinds ofmeasurement report triggering conditions. Among them, the most widelyused measurement report triggering condition is an Event A3 describedabove.

A Mobility Management Entity (MME) 240 or a serving gateway 250 has arearestriction information at step A.

A source eNB 220 sends a measurement control message to a UE 210 toprovide several values necessary for measurement report triggeringperformance to the UE 210 at step B.

One of the provided values is a TTT value. The measurement controlmessage means an RRC connection reconfiguration message, including aMeasConfig Information Element (IE) in the LTE system.

An Event A3 takes place if a leaving condition is not met during a TTTtime after an entering condition of the Event A3 is met. Here, the TTTvalue means a time having to meet the measurement report triggeringcondition (i.e., the Event A3) in order to trigger a measurement reportevent. The TTT value is described below in more detail.

First, if the entering condition is met, the UE 210 operates a TTTrelated timer. After that, if the UE 210 continues to meet the enteringcondition during the TTT time, the UE 210 sends a measurement reportmessage to the serving or source eNB 220 at step C.

If the entering condition is not met within the TTT time, the TTTrelated timer is reset to a first TTT value. If the leaving condition ismet, the TTT related timer is released.

If the source eNB 220 receives the measurement report message from theUE 210, the source eNB 220 determines whether to allow the UE 210 toperform handover to a target eNB 230 with reference to RRM informationat step D.

Henceforth, a process in which an idle mode UE performs cell reselectiontriggering is described below.

In a case where a UE operates in an idle mode, the idle mode UE performsmeasurement for the sake of cell reselection. Generally, the idle modeUE determines cell reselection performance or non-performance.Measurement rules for cell reselection triggering performance in the LTEsystem are given as follows.

If ‘SServingCell’ is less than ‘Sintrasearch’ or if the ‘Sintrasearch’is not forwarded to a serving cell, the idle mode UE performsintra-frequency measurements. If the ‘Sintrasearch’ is forwarded to theserving cell and the ‘SServingCell’ is greater than the ‘Sintrasearch’,the UE is no longer required to perform intra-frequency measurements.

Here, the ‘SServingCell’ represents a received signal level value (unitis dB) of the serving cell, and the ‘Sintrasearch’ represents athreshold value (unit is dB) for intra-frequency measurements. ATreselection value for an idle mode UE performs a role similar to a TTTvalue for an active mode UE.

The Treselection value is described below in more detail. First, if acell reselection triggering condition is met, a UE operates aTreselection related timer.

After that, if the cell reselection triggering condition continues to bemet during a Treselection time, the UE performs a cell reselectionprocess. If the cell reselection triggering condition is not met withinthe Treselection time, the Treselection related timer is reset to afirst Treselection value.

FIG. 3 is a diagram illustrating a change of DownLink (DL) receivedsignal strength at a handover from a macro cell to a micro cellaccording to an exemplary embodiment of the present invention.

Referring to FIG. 3, in a case where a macro cell 310 and a micro cell320 operate in the same frequency under an environment in which themicro cell 320 is overlapped within the macro cell 310, when a UE 300performs handover from the macro cell 310 to the micro cell 320,interference from a micro eNB of the micro cell 320 quickly increasesnear a micro cell 320 boundary, and a channel environment suddenlydeteriorates.

Also, the UE 300 exerts significant UpLink (UL) interference to themicro eNB of the micro cell 320. That is because a path loss between themicro eNB of the micro cell 320 and the UE 300 varies quickly comparedto a path loss between a macro eNB of the macro cell 310 and the UE 300.So, the UE 300 suffers a Radio Link Failure (RLF) before performinghandover to the micro cell 320.

More particularly, in a case where the UE 300 moving at high speedperforms handover from the macro cell 310 to the micro cell 320, if arelatively long TTT parameter value applied to handover performancebetween the macro cells 310 is applied to the handover from the macrocell 310 to the micro cell 320 as it is, the handover from the macrocell 310 to the micro cell 320 is delayed and a probability of RLFoccurrence increases suddenly.

In order to address this problem, there is a need to apply a separateparameter (i.e., a handover trigger threshold and a TTT) suitable tohandover carried out between the macro cell 310 and the micro cell 320.

In order to support stable handover between the macro cell 310 and themicro cell 320, the following two items should be all met.

First, a serving eNB should be able to apply a handover triggerthreshold value and a TTT value independently by a neighboring targeteNB and forward these parameter values to a UE. That is, the serving eNBshould be able to apply separate handover trigger threshold and TTTvalues by a Physical Cell Identifier (PCI) of a handover target eNB andforward these parameter values to the UE.

This means that the serving eNB can apply the handover trigger thresholdvalue and TTT value differently depending on whether the target eNB isthe macro eNB of the macro cell 310 or is the micro eNB of the microcell 320, and forward these parameter values to the UE 300.

Second, the serving eNB should know whether it must apply which handovertrigger threshold value and TTT value by neighboring target eNB. Thatcan meet the first requirement. The current standard of the related arthas not yet proposed a way for negotiating a TTT value between eNBs.

These problems are presented in FIGS. 4, 5, and 6, to be describedbelow. Here, the handover trigger threshold value means an offset valuein an Event A3.

FIG. 4 is a diagram illustrating an HO process dependent on a positionof a UE when the UE performs handover from a macro cell to a macro cellaccording to an exemplary embodiment of the present invention.

Referring to FIG. 4, in a case where a UE performs handover from a macrocell 1 (P1) to a macro cell 2 (P2), an Event A3 occurs when an HOthreshold value between the macro cells 1 and 2 is greater than an HOthreshold at step 1. When the Event A3 is maintained for more than a TTTvalue at step 2, the UE sends a measurement report message to the macrocell 1 at step 3. In response to this, the macro cell 1 determineshandover or non-handover of the UE and sends an HO command message tothe UE at step 4.

FIG. 5 is a diagram illustrating an HO process dependent on a positionof a UE when the UE performs handover from a macro cell to a micro cellaccording to an exemplary embodiment of the present invention.

Referring to FIG. 5, steps 1-3 are the same as in FIG. 4. In a casewhere an HO process at steps 1 to 4 uses a parameter applied at handoverfrom a macro cell to a macro cell as it is, an HO failure takes placeowing to sudden interference at step 4.

FIG. 6 is a diagram illustrating an HO process dependent on a positionof a UE when the UE performs handover from a macro cell to a micro cellaccording to another exemplary embodiment of the present invention.

Referring to FIG. 6, an HO process at steps 1 to 4 applies a parameteroptimized to handover from a macro cell 1 (P1) to a micro cell 2 (P2).As seen in FIG. 6, before sudden interference reception, the handover ofa UE to the micro cell 2 (P2) is made quickly at steps 1 and 2, and thusan HO success at steps 3 and 4 is made.

As aforementioned, in order to support stable handover between a macrocell and a micro cell, a serving eNB should be able to apply a handovertrigger threshold value and a TTT value independently by a neighboringeNB, and forward these parameter values to a UE.

That is, the serving eNB should be able to apply separate handovertrigger threshold value and TTT value by PCI of an HO target eNB, andforward these parameter values to the UE. So, the serving eNB can makean HO success if the UE applies the handover trigger threshold value andTTT value differently depending on whether the HO target eNB is a macroeNB or a micro eNB, and sends a measurement report message to theserving eNB.

The handover trigger threshold value is presented as a‘cellIndividualoffset’ value in a MeasObjectEUTRA IE. TheMeasObjectEUTRA IE includes information necessary when an active mode UEdetermines neighboring cells.

However, in the current LTE standard, a serving eNB cannot forward a TTTvalue by a neighboring eNB to a UE. Like the TTT value, in the currentLTE standard, the serving eNB cannot forward even a Treselection valueindependently by a neighboring eNB to the UE.

As described above, exemplary embodiments of the present inventionprovide an apparatus and method for negotiating TTT related informationbetween eNBs through an X2 interface in a 3GPP LTE based system.

According to the LTE standard, a ‘mobility settings procedure’ isdefined as one of elementary procedures. This procedure is a procedurein which, when desiring to change a mobility related parameter, an eNBnegotiates the mobility related parameter to be changed with aneighboring eNB through the X2 interface.

Through the procedure, the current standard can perform a function ofnegotiating a change value of a handover trigger threshold for thepurpose of load balancing between eNBs, HO optimization, and the like.

An exemplary embodiment of the present invention uses the ‘mobilitysettings procedure’ for TTT related information negotiation between eNBsthrough an X2 interface.

However, the present invention is not limited to using the X2 interfacefor the TTT related information negotiation and providing between eNBs.Any scheme for the TTT related information negotiation and providingbetween eNBs may be used.

FIG. 7 is a ladder diagram illustrating a mobility change process of aneNB according to an exemplary embodiment of the present invention.

Referring to FIG. 7, to provide optimized TTT related information, aneNB1 710 sends a mobility change request message to an eNB2 720connected through an X2 interface and a UE intending to perform handoverfrom the eNB2 720 to the eNB1 710 at step A.

That is, the mobility change request message includes TTT relatedinformation optimized to its own cell. After the eNB2 720 receives themobility change request message, the eNB2 720 determines whether the TTTrelated information included in the mobility change request message isan acceptable value.

If the eNB2 720 determines that the TTT related information is theacceptable value, the eNB2 720 forwards a mobility change acknowledgemessage as a response message to the eNB1 710 at step B. If the eNB2 720does not accept the requested TTT related information, the eNB2 720sends a mobility change failure message to the eNB1 710 at step B.

By the following two methods, the TTT related information can be addedwithin the mobility change request message. The mobility change requestmessage of the current LTE standard includes an IE called ‘eNB2 ProposedMobility Parameters’. This IE represents that the mobility changerequest message includes an IE called ‘Mobility Parameters Information’that is mobility related parameter information to be used for handoverthat the eNB1 710 provides to the eNB2 720, and is shown in Table 1below.

TABLE 1 IE/Group Pres- Semantics Name ence Range IE type and Referencedescription Handover M INTEGER The actual Trigger (−20 . . . 20) valueis IE Change value * 0.5 dB

Here, the ‘Handover Trigger Change’ means a change value for thisthreshold.

An exemplary embodiment of the present invention provides two ways forforwarding TTT related information.

First, a method for expressing TTT related information by a ‘dB’ valueand negotiating the TTT related information is described below.

This method is a method for allowing an existing handover trigger changeto express a TTT as well as a threshold. For this, an exemplaryembodiment of the present invention proposes adding a handover triggertype IE to a mobility parameters information IE. So, the mobilityparameters information IE reflecting this is shown in Table 2 below.

TABLE 2 IE/Group Pres- Semantics Name ence Range IE type and Referencedescription Handover M INTEGER The actual Trigger (−20 . . . 20) valueis IE Change value * 0.5 dB Handover M ENUMERATED Trigger {Threshold,Type TimeToTrigger . . .}

For example, regarding the mobility parameters information IEcorresponding to proposed mobility parameters of a mobility changerequest message, the eNB1 710 sets the handover trigger change to −3 dBand sets the handover trigger type to ‘TimeToTrigger’, and transmits thehandover trigger change and the handover trigger type to the eNB2 720.If the eNB2 720 accepts this, the eNB2 720 reduces the TTT value for theeNB1 710 to 0.5 times of the current value.

The TTT value of the LTE standard is within a range of ms0, ms40, ms64,ms80, ms100, ms128, ms160, ms256, ms320, ms480, ms512, ms640, ms1024,ms1280, ms2560, and ms5120, and how to change the TTT value depending onthe ‘dB’ value varies according to a realization scheme.

Second, a method for expressing TTT related information by an absolutevalue and negotiating the TTT related information is described below.

This method is a method for, regarding a handover trigger change,assuming that it is a change value for a threshold and, regarding a TTT,adding a new IE negotiate an absolute value. The IE is designated to oneof TTT1 ms, TTT2 ms, . . . , TTTn ms. The mobility parametersinformation IE reflecting this is shown in Table 3 below.

TABLE 3 IE/Group Pres- Semantics Name ence Range IE type and Referencedescription Handover 0 INTEGER The actual Trigger (−20 . . . 20) valueis IE Change value * 0.5 dB Time To 0 ENUMERATED Unit is ms. Trigger{TTT1, TTT2, . . . , TTTn}

FIG. 8 is a flowchart illustrating a mobility change process of an eNBaccording to an exemplary embodiment of the present invention.

Referring to FIG. 8, when an event of transmitting a TTT or threshold(i.e., handover trigger threshold) value takes place at step 810, theeNB transmits the TTT or threshold (handover trigger threshold) value toa neighboring eNB (i.e., a corresponding eNB) at step 820.

Here, the transmitting event can be a case where the TTT or threshold(i.e., handover trigger threshold) value for the corresponding eNB ischanged, a case where a new eNB is added and the new eNB transmits, andthe like.

An exemplary embodiment of the present invention proposes a way for aserving eNB to forward TTT and Treselection values independently by aneighboring eNB to a UE in an LTE system.

FIG. 9 is a message flow diagram illustrating a process of forwardingTTT and Treselection values independently by a neighboring eNB to a UEin a serving eNB according to an exemplary embodiment of the presentinvention.

Referring to FIG. 9, the serving eNB 910 transmits a TTT or aTTT-Scaling Factor (SF)/a Treselection or a Treselection-SF to an activemode or idle mode UE 920 at step A. This is described below in detail.

FIG. 10 is a flowchart illustrating a process of forwarding TTT andTreselection values independently by a neighboring eNB to a UE in aserving eNB according to an exemplary embodiment of the presentinvention.

Referring to FIG. 10, when an object is an active mode UE at step 1010and division is made according to a cell type at step 1015, the servingeNB sets and transmits a TTT value or a TTT-SF value independently by aneighboring cell belonging to a specific cell type at step 1025.

When the object is the active mode UE at step 1010 and division is notmade according to the cell type at step 1515, the serving eNB sets andtransmits a TTT value or a TTT-SF value independently by a specificneighboring cell at step 1020.

When the object is not the active mode UE but an idle mode UE at step1010 and division is made according to the cell type at step 1030, theserving eNB sets and transmits a Treselection value or a Treselection-SFvalue independently by a neighboring cell belonging to a specific celltype step 1040.

When the object is the idle mode UE at step 1010 and the division is notmade according to the cell type at step 1030, the serving eNB sets andtransmits a Treselection value or a Treselection-SF value independentlyby a specific neighboring cell at step 1035.

A way for a serving eNB to forward a TTT value independently by aneighboring eNB to an active mode UE is described below.

Table 4 illustrates a case of setting a TTT value independently by aspecific neighboring cell according to an exemplary embodiment of thepresent invention. Table 4 relates to a method (1-1) for setting a TTTvalue independently by a specific neighboring cell. In an LTE system ofthe related art, a MeasObjectEUTRA IE includes information necessarywhen an active mode UE determines neighboring cells.

TABLE 4 MeasObjectEUTRA information element -- ASN1START MeasObjectEUTRA::= SEQUENCE { carrierFreq ARFCN-ValueEUTRA, allowedMeasBandwidthAllowedMeasBandwidth, presenceAntennaPort1 PresenceAntennaPort1,neighCellConfig NeighCellConfig, offsetFreq Q-OffsetRange DEFAULT dB0,-- Neighbour cell list cellsToRemoveList CellIndexList OPTIONAL,  --Need ON cellsToAddModList CellsToAddModList OPTIONAL,  -- Need ON --Black list blackCellsToRemoveList CellIndexList OPTIONAL,  -- Need ONblackCellsToAddModList BlackCellsToAddModList OPTIONAL,  -- Need ONcellForWhichToReportCGI PhysCellId OPTIONAL,  -- Need ON ... }CellsToAddModList ::= SEQUENCE (SIZE (1..maxCellMeas)) OF CellsToAddModCellsToAddMod ::= SEQUENCE { cellIndex INTEGER (1..maxCellMeas),physCellId PhysCellId, cellIndividualOffset Q-OffsetRange,cellIndividualTimeToTrigger TimeToTrigger OPTIONAL, -- Need ON }BlackCellsToAddModList ::= SEQUENCE (SIZE (1..maxCellMeas)) OFBlackCellsToAddMod BlackCellsToAddMod ::= SEQUENCE { cellIndex INTEGER(1..maxCellMeas), physCellIdRange PhysCellIdRange } -- ASN1STOP

Table 4 adds a ‘cellIndividualTimeToTrigger’ field shown in ahighlighted color, to the ‘MeasObjectEUTRA’ IE. The added‘cellIndividualTimeToTrigger’ field represents a cell individual TTTvalue applied to a specific neighboring cell.

Similar to the ‘cellIndividualOffset’ field of the related art, the‘cellIndividualTimeToTrigger’ field becomes a measurement reporttriggering related parameter applied independently by neighboring cell.So, a UE can apply a TTT value independently by a neighboring eNB. The‘cellIndividualTimeToTrigger’ is shown in Table 5 below.

TABLE 5 cellIndividualTimeToTrigger Cell individual time to triggerparameter applicable to a specific neighboring cell.

Table 6 illustrates a case of setting a TTT-SF value independently by aspecific neighboring cell according to an exemplary embodiment of thepresent invention but applying and setting SF values set considering anexisting speed state of a UE. Table 6 relates to a method (1-2) forsetting a TTT-SF value independently by a specific neighboring cell.

TABLE 6 MeasObjectEUTRA information element -- ASN1START MeasObjectEUTRA::= SEQUENCE { carrierFreq ARFCN-ValueEUTRA, allowedMeasBandwidthAllowedMeasBandwidth, presenceAntennaPort1 PresenceAntennaPort1,neighCellConfig NeighCellConfig, offsetFreq Q-OffsetRange DEFAULT dB0,-- Neighbour cell list cellsToRemoveList CellIndexList OPTIONAL,  --Need ON cellsToAddModList CellsToAddModList OPTIONAL,  -- Need ON --Black list blackCellsToRemoveList CellIndexList OPTIONAL,  -- Need ONblackCellsToAddModList BlackCellsToAddModList OPTIONAL,  -- Need ONcellForWhichToReportCGI PhysCellId OPTIONAL,  -- Need ON ... }CellsToAddModList ::= SEQUENCE (SIZE (1..maxCellMeas)) OF CellsToAddModCellsToAddMod ::= SEQUENCE { cellIndex INTEGER (1..maxCellMeas),physCellId PhysCellId, cellIndividualOffset Q-OffsetRange,cellIndividualTimeToTrigger TimeToTrigger OPTIONAL, -- Need ON }BlackCellsToAddModList ::= SEQUENCE (SIZE (1..maxCellMeas)) OFBlackCellsToAddMod BlackCellsToAddMod ::= SEQUENCE { cellIndex INTEGER(1..maxCellMeas), physCellIdRange PhysCellIdRange } -- ASN1STOP

The current LTE standard of the related art applies a ‘speed-dependent’SF according to a speed of a UE.

In a case where an active mode UE has high and medium mobility, Table 6multiplies a TTT by an SF-High value and an SF-Medium value,respectively.

So, in a case where a UE is fast, Table 6 can apply a TTT value lessthan an originally given TTT value. That is because, if the UE is fast,the TTT must be set lower to increase a HO success ratio.

This method can also reuse and apply SF values set considering a speedstate of a UE presented in the current LTE standard as it is, or cannewly set separate SF values.

More particularly, Table 6 relates to a method (1-2-1) for applying andsetting SF values set considering an existing speed state of a UE, andadds a ‘cellIndividualTimeToTrigger-SF’ field shown in a highlightedcolor to a MeasObjectEUTRA IE.

The added ‘cellIndividualTimeToTrigger-SF’ field means a cell individualTTT-SF value applied to a specific neighboring cell. In the case of thespecific neighboring cell, Table 6 can multiply an originally given TTTvalue by the SF value and set a TTT short.

Here, Table 6 applies a SpeedStateScaleFactors IE that includes SFvalues set considering a speed state of a UE presented in the currentLTE standard of the related art, as it is. And, aCelllndividualTimeToTrigger-SF is shown in Table 7 below.

TABLE 7 CellIndividualTimeToTrigger-SF Cell individual scaling factorapplicable to a specific neighboring cell. The TimeToTrigger inReportConfigEUTRA is multiplied by this scaling factor.

Table 8 illustrates a case (1-2-2) of setting a TTT-SF valueindependently by a specific neighboring cell according to an exemplaryembodiment of the present invention but newly setting separate SFvalues. Table 8 adds a ‘cellIndividualTimeToTrigger-SF’ field shown in ahighlighted color to a MeasObjectEUTRA IE.

TABLE 8 MeasObjectEUTRA information element -- ASN1START MeasObjectEUTRA::= SEQUENCE { carrierFreq ARFCN-ValueEUTRA, allowedMeasBandwidthAllowedMeasBandwidth, presenceAntennaPort1 PresenceAntennaPort1,neighCellConfig NeighCellConfig, offsetFreq Q-OffsetRange DEFAULT dB0,-- Neighbour cell list cellsToRemoveList CellIndexList OPTIONAL,  --Need ON cellsToAddModList CellsToAddModList OPTIONAL,  -- Need ON --Black list blackCellsToRemoveList CellIndexList OPTIONAL,  -- Need ONblackCellsToAddModList BlackCellsToAddModList OPTIONAL,  -- Need ONcellForWhichToReportCGI PhysCellId OPTIONAL,  -- Need ON ... }CellsToAddModList ::= SEQUENCE (SIZE (1..maxCellMeas)) OF CellsToAddModCellsToAddMod ::= SEQUENCE { cellIndex INTEGER (1..maxCellMeas),physCellId PhysCellId, cellIndividualOffset Q-OffsetRange,cellIndividualTimeToTrigger-SF SpeedStateScaleFactors OPTIONAL, -- NeedON } BlackCellsToAddModList ::= SEQUENCE (SIZE (1..maxCellMeas)) OFBlackCellsToAddMod BlackCellsToAddMod ::= SEQUENCE { cellIndex INTEGER(1..maxCellMeas), physCellIdRange PhysCellIdRange } -- ASN1STOP

The added ‘cellIndividualTimeToTrigger-SF’ field means a cell individualTTT-SF value applied to a specific neighboring cell. In the case of thespecific neighboring cell, Table 8 can multiply an originally given TTTvalue by the SF value and set a TTT short.

Here, Table 8 uses a CellIndividualScaleFactors IE that is an SF relatedIE newly defined in an exemplary embodiment of the present invention.The CelllndividualTimeToTrigger-SF is shown in Table 9 below.

TABLE 9 CellIndividualTimeToTrigger-SF Cell individual scaling factorapplicable to a specific neighboring cell. The TimeToTrigger inReportConfigEUTRA is multiplied by this scaling factor.

And, the CellIndividualScaleFactors IE is given as follows.

CellIndividualScaleFactors information element -- ASN1STARTCellIndividualScaleFactors ::= ENUMERATED (x_1, x_2, . . . , x_n) --ASN1STOP

Here, ‘x_1’, ‘x_2’, . . . , ‘x_n’ values are mapped to values of 0 to 1.

Table 10 represents a way for setting, to a MeasObjectEUTRA IE, a TTTvalue independently by neighboring cells belonging to a specific celltype according to an exemplary embodiment of the present invention.

Table 10 relates to a method (1-3) for setting a TTT value independentlyby neighboring cells belonging to a specific cell type. Table 10 can set(1-3-1), to a MeasObjectEUTRA IE, a TTT value independently byneighboring cells belonging to a specific cell type.

TABLE 10 MeasObjectEUTRA information element -- ASN1STARTMeasObjectEUTRA ::= SEQUENCE { carrierFreq ARFCN-ValueEUTRA,allowedMeasBandwidth AllowedMeasBandwidth, presenceAntennaPort1PresenceAntennaPort1, neighCellConfig NeighCellConfig, offsetFreqQ-OffsetRange DEFAULT dB0, -- Neighbour cell list cellsToRemoveListCellIndexList OPTIONAL,  -- Need ON cellsToAddModList CellsToAddModListOPTIONAL,  -- Need ON -- Black list blackCellsToRemoveList CellIndexListOPTIONAL,  -- Need ON blackCellsToAddModList BlackCellsToAddModListOPTIONAL,  -- Need ON cellForWhichToReportCGI PhysCellId OPTIONAL,  --Need ON ... } CellsToAddModList ::= SEQUENCE (SIZE (1..maxCellMeas)) OFCellsToAddMod CellsToAddMod ::= SEQUENCE { cellIndex INTEGER(1..maxCellMeas), physCellId PhysCellId, cellIndividualOffsetQ-OffsetRange, cellTypesList CellTypesList OPTIONAL -- Need ON }BlackCellsToAddModList ::= SEQUENCE (SIZE (1..maxCellMeas)) OFBlackCellsToAddMod BlackCellsToAddMod ::= SEQUENCE { cellIndex INTEGER(1..maxCellMeas), physCellIdRange PhysCellIdRange } CellTypesList ::=SEQUENCE (SIZE (1..maxCellTypes)) OF CellTypes CellTypes ::= SEQUENCE {physCellIdRange PhysCellIdRange, timeToTrigger TimeToTrigger } --ASN1STOP

First, when considering a case of setting to a MeasObjectEUTRA IE, Table10 newly proposes a ‘CellTypeList’ field shown in a highlighted color inthe MeasObjectEUTRA IE. The ‘CellTypeList’ field is designed to have TTTvalues different from each other every PCI range of a different celltype. A cell type list is shown in Table 11 below.

TABLE 11 CellTypesList List of cell types having individual differenttime which specific criteria for the event needs to be met in order totrigger a measurement report.

Table 12 represents a way for setting, to a ReportConfigEUTRA IE, a TTTvalue independently by a neighboring cell belonging to a specific celltype according to an exemplary embodiment of the present invention.

Table 12 relates to a method (1-3) for setting a TTT value independentlyby neighboring cells belonging to a specific cell type. Table 12 can set(1-3-2), to a ReportConfigEUTRA IE, the TTT value independently byneighboring cells belonging to the specific cell type.

TABLE 12 ReportConfigEUTRA information element -- ASN1STARTReportConfigEUTRA ::= SEQUENCE { triggerType CHOICE { event SEQUENCE {eventId CHOICE { eventA1 SEQUENCE { a1-Threshold ThresholdEUTRA },eventA2 SEQUENCE { a2-Threshold ThresholdEUTRA }, eventA3 SEQUENCE {a3-Offset INTEGER (−30..30), reportOnLeave BOOLEAN }, eventA4 SEQUENCE {a4-Threshold ThresholdEUTRA }, eventA5 SEQUENCE { a5-Threshold1ThresholdEUTRA, a5-Threshold2 ThresholdEUTRA }, ... }, hysteresisHysteresis, timeToTrigger TimeToTrigger, cellTypesList CellTypesListOPTIONAL --Need ON }, periodical SEQUENCE { purpose ENUMERATED {reportStrongestCells, reportCGI} } }, triggerQuantity ENUMERATED {rsrp,rsrq}, reportQuantity ENUMERATED {sameAsTriggerQuantity, both},maxReportCells INTEGER (1..maxCellReport), reportIntervalReportInterval, reportAmount ENUMERATED {r1, r2, r4, r8, r16, r32, r64,infinity}, ..., reportConfigEUTRA-v9x0 ReportConfigEUTRA-v9x0-IEsOPTIONAL --Need ON } CellTypesList ::= SEQUENCE (SIZE (1..maxCellTypes))OF CellTypes CellTypes ::= SEQUENCE { physCellIdRange PhysCellIdRange,timeToTrigger TimeToTrigger }

Table 12 newly proposes a ‘CellTypeList’ field shown in a highlightedcolor in the ReportConfigEUTRA IE. The ‘CellTypeList’ field is designedto have a TTT value different from each other every PCI range of adifferent cell type. Here, a cell type list is shown in Table 13 below.

TABLE 13 CellTypesList List of cell types having individual differenttime which specific criteria for the event needs to be met in order totrigger a measurement report.

Table 14 illustrates a case of applying SF values set considering anexisting speed state of a UE and setting, to a MeasObjectEUTRA IE, aTTT-SF value independently by neighboring cells belonging to a specificcell type according to an exemplary embodiment of the present invention.

TABLE 14 MeasObjectEUTRA information element -- ASN1STARTMeasObjectEUTRA ::= SEQUENCE { carrierFreq ARFCN-ValueEUTRA,allowedMeasBandwidth AllowedMeasBandwidth, presenceAntennaPort1PresenceAntennaPort1, neighCellConfig NeighCellConfig, offsetFreqQ-OffsetRange DEFAULT dB0, -- Neighbour cell list cellsToRemoveListCellIndexList OPTIONAL,  -- Need ON cellsToAddModList CellsToAddModListOPTIONAL,  -- Need ON -- Black list blackCellsToRemoveList CellIndexListOPTIONAL,  -- Need ON blackCellsToAddModList BlackCellsToAddModListOPTIONAL,  -- Need ON cellForWhichToReportCGI PhysCellId OPTIONAL,  --Need ON ... } CellsToAddModList ::= SEQUENCE (SIZE (1..maxCellMeas)) OFCellsToAddMod CellsToAddMod ::= SEQUENCE { cellIndex INTEGER(1..maxCellMeas), physCellId PhysCellId, cellIndividualOffsetQ-offsetRange, cellTypesList CellTypesList OPTIONAL -- Need ON }BlackCellsToAddModList ::= SEQUENCE (SIZE (1..maxCellMeas)) OFBlackCellsToAddMod BlackCellsToAddMod ::= SEQUENCE { cellIndex INTEGER(1..maxCellMeas), physCellIdRange PhysCellIdRange } CellTypesList ::=SEQUENCE (SIZE (1..maxCellTypes)) OF CellTypes CellTypes ::= SEQUENCE {physCellIdRange PhysCellIdRange, timeToTrigger-SFSpeedStaterScaleFactors } -- ASN1STOP

Table 14 relates to a method (1-4) for setting a TTT-SF valueindependently by neighboring cells belonging to a specific cell type.The TTT-SF value independently by neighboring cells belonging to thespecific cell type can be set to a MeasObjectEUTRA IE (1-4-1) or aReportConfigEUTRA IE (1-4-2).

Table 14 newly proposes a ‘CellTypeList’ field shown in a highlightedcolor in the MeasObjectEUTRA IE. The ‘CellTypeList’ field is designed tohave TTT-SF values different from each other every PCI range of adifferent cell type.

As in the example (1-2), even this example (1-4-1) can apply (1-4-1-1)reusing, as it is, SF values set considering a speed state of a UEpresented in the current LTE standard. Here, a cell type list is shownin Table 15 below.

TABLE 15 CellTypesList List of cell types having individual scalingfactor applicable to a neighboring cell(s) belonging to a specific celltype. The TimeToTrigger in ReportConfigEUTRA is multiplied by thisscaling factor.

Table 16 represents a case of newly setting, to a MeasObjectEUTRA IE, aTTT-SF value independently by neighboring cells belonging to a specificcell type according to an exemplary embodiment of the present invention.

TABLE 16 MeasObjectEUTRA information element -- ASN1STARTMeasObjectEUTRA ::= SEQUENCE { carrierFreq ARFCN-ValueEUTRA,allowedMeasBandwidth AllowedMeasBandwidth, presenceAntennaPort1PresenceAntennaPort1, neighCellConfig NeighCellConfig, offsetFreqQ-OffsetRange DEFAULT dB0, -- Neighbour cell list cellsToRemoveListCellIndexList OPTIONAL,  -- Need ON cellsToAddModList CellsToAddModListOPTIONAL,  -- Need ON -- Black list blackCellsToRemoveList CellIndexListOPTIONAL,  -- Need ON blackCellsToAddModList BlackCellsToAddModListOPTIONAL,  -- Need ON cellForWhichToReportCGI PhysCellId OPTIONAL,  --Need ON ... } CellsToAddModList ::= SEQUENCE (SIZE (1..maxCellMeas)) OFCellsToAddMod CellsToAddMod ::= SEQUENCE { cellIndex INTEGER(1..maxCellMeas), physCellId PhysCellId, cellIndividualOffsetQ-OffsetRange, cellTypesList CellTypesList OPTIONAL -- Need ON }BlackCellsToAddModList ::= SEQUENCE (SIZE (1..maxCellMeas)) OFBlackCellsToAddMod BlackCellsToAddMod ::= SEQUENCE { cellIndex INTEGER(1..maxCellMeas), physCellIdRange PhysCellIdRange } CellTypeList ::=SEQUENCE (SIZE (1..maxCellTypes)) OF CellTypes CellTypes ::= SEQUENCE {physCellIdRange PhysCellIdRange, timeToTrigger-SFCellIndividualScaleFactors } -- ASN1STOP

Table 16 relates to a method for setting a TTT-SF value independently byneighboring cells belonging to a specific cell type. The TTT-SF valueindependently by neighboring cells belonging to the specific cell typecan be set to a MeasObjectEUTRA IE (1-4-1) or a ReportConfigEUTRA IE(1-4-2).

Table 16 newly proposes a ‘CellTypeList’ field shown in a highlightedcolor in the MeasObjectEUTRA IE. The ‘CellTypeList’ field is designed tohave TTT-SF values different from each other every PCI range of adifferent cell type.

Similar to the example (1-2), even this example (1-4-1) can also newlyset (1-4-1-2) separate SF values considering a speed state of a UEpresented in the current LTE standard of the related art. Here, a celltype list is shown in Table 17 below.

TABLE 17 CellTypesList List of cell types having individual scalingfactor applicable to a neighboring cell(s) belonging to a specific celltype. The TimeToTrigger in ReportConfigEUTRA is multiplied by thisscaling factor. CellIndividualScaleFactors information element --ASN1START CellIndividualScaleFactors ::= ENUMERATED (x_1, x_2, . . . ,x_n) -- ASN1STOP

Here, ‘x_1’, ‘x_2’, . . . , ‘x_n’ values are mapped to values of 0 to 1.

Table 18 represents a case of applying SF values set considering anexisting speed state of a UE and setting, to a ReportConfigEUTRA IE, aTTT-SF independently by neighboring cells belonging to a specific celltype according to an exemplary embodiment of the present invention.

This relates to a method (1-4) for setting a TTT-SF value independentlyby neighboring cells belonging to a specific cell type. The TTT-SF valueindependently by neighboring cells belonging to the specific cell typecan be set to the MeasObjectEUTRA IE (1-4-1) or the ReportConfigEUTRA IE(1-4-2).

TABLE 18 ReportConfigEUTRA information element -- ASN1STARTReportConfigEUTRA ::= SEQUENCE { triggerType CHOICE { event SEQUENCE {eventId CHOICE { eventA1 SEQUENCE { a1-Threshold ThresholdEUTRA },eventA2 SEQUENCE { a2-Threshold ThresholdEUTRA }, eventA3 SEQUENCE {a3-Offset INTEGER (−30..30), reportOnLeave BOOLEAN }, eventA4 SEQUENCE {a4-Threshold ThresholdEUTRA }, eventA5 SEQUENCE { a5-Threshold1ThresholdEUTRA, a5-Threshold2 ThresholdEUTRA }, ... }, hysteresisHysteresis, timeToTrigger TimeToTrigger, cellTypeList CellTypesListOPTIONAL --Need ON }, periodical SEQUENCE { purpose ENUMERATED {reportStrongestCells, reportCGI} } }, triggerQuantity ENUMERATED {rsrp,rsrq}, reportQuantity ENUMERATED {sameAsTriggerQuantity, both},maxReportCells INTEGER (1..maxCellReport), reportIntervalReportInterval, reportAmount ENUMERATED {r1, r2, r4, r8, r16, r32, r64,infinity}, ..., reportConfigEUTRA-v9x0 ReportConfigEUTRA-v9x0-IEsOPTIONAL --Need ON } CellTypesList ::= SEQUENCE (SIZE (1..maxCellTypes))OF CellTypes CellTypes ::= SEQUENCE { physCellIdRange PhysCellIdRange,timeToTrigger SpeedStateScaleFactors }

In Table 18 above, an exemplary embodiment of the present inventionnewly proposes a ‘CellTypeList’ field shown in a highlighted color inthe ReportConfigEUTRA IE. The ‘CellTypeList’ field is designed to haveTTT-SF values different from each other every PCI range of a differentcell type.

Similar to the example (1-2), even this example (1-4-2) can also applyreusing SF values set considering a speed state of a UE presented in thecurrent LTE standard of the related art. Here, a cell type list is shownin Table 19.

TABLE 19 CellTypesList List of cell types having individual scalingfactor applicable to a neighboring cell(s) belonging to a specific celltype. The TimeToTrigger in ReportConfigEUTRA is multiplied by thisscaling factor.

Table 20 represents a case of newly setting, to a ReportConfigEUTRA IE,a TTT-SF value independently by neighboring cells belonging to aspecific cell type according to an exemplary embodiment of the presentinvention.

Table 20 is about a way (1-4) for setting a TTT-SF value independentlyby neighboring cells belonging to a specific cell type. The TTT-SF valueindependently by neighboring cells belonging to the specific cell typecan be set to a MeasObjectEUTRA IE (1-4-1) or a ReportConfigEUTRA IE(1-4-2).

TABLE 20 ReportConfigEUTRA information element -- ASN1STARTReportConfigEUTRA ::= SEQUENCE { triggerType CHOICE { event SEQUENCE {eventId CHOICE { eventA1 SEQUENCE { a1-Threshold ThresholdEUTRA },eventA2 SEQUENCE { a2-Threshold ThresholdEUTRA }, eventA3 SEQUENCE {a3-Offset INTEGER (−30..30), reportOnLeave BOOLEAN }, eventA4 SEQUENCE {a4-Threshold ThresholdEUTRA }, eventA5 SEQUENCE { a5-Threshold1ThresholdEUTRA, a5-Threshold2 ThresholdEUTRA }, ... }, hysteresisHysteresis, timeToTrigger TimeToTrigger, cellTypesList CellTypesListOPTIONAL --Need ON }, periodical SEQUENCE { purpose ENUMERATED {reportStrongestCells, reportCGI} } }, triggerQuantity ENUMERATED {rsrp,rsrq}, reportQuantity ENUMERATED {sameAsTriggerQuantity, both},maxReportCells INTEGER (1..maxCellReport), reportIntervalReportInterval, reportAmount ENUMERATED {r1, r2, r4, r8, r16, r32, r64,infinity}, ..., reportConfigEUTRA-v9x0 ReportConfigEUTRA-v9x0-IEsOPTIONAL --Need ON } CellTypesList ::= SEQUENCE (SIZE (1..maxCellTypes))OF CellTypes CellTypes ::= SEQUENCE { physcellIdRange PhysCellIdRange,timetoTrigger CellIndividualScaleFactors }

As in Table 20, an exemplary embodiment of the present invention newlyproposes a ‘CellTypeList’ field shown in a highlighted color in theReportConfigEUTRA IE. The ‘CellTypeList’ field is designed to haveTTT-SF values different from each other every PCI range of a differentcell type.

Similar to the example (1-2), even this example (1-4-2) can also newlyset separate SF values considering a speed state of a UE presented inthe current LTE standard of the related art. Here, a cell type list isshown in Table 21 below.

TABLE 21 CellTypesList List of cell types having individual scalingfactor applicable to a neighboring cell(s) belonging to a specific celltype. The TimeToTrigger in ReportConfigEUTRA is multiplied by thisscaling factor. CellIndividualScaleFactors information element --ASN1START CellIndividualScaleFactors ::= ENUMERATED (x_1, x_2, . . . ,x_n) -- ASN1STOP

Here, ‘x_1’, ‘x_2’, . . . , ‘x_n’ values are mapped to values of 0 to 1.

(2) A way for a serving eNB to forward a Treselection valueindependently by a neighboring eNB to an idle mode UE is describedbelow.

Table 22 represents a case of setting a Treselection value independentlyby a specific neighboring cell according to an exemplary embodiment ofthe present invention.

Table 22 relates to a method (2-1) of setting the Treselection valueindependently by a specific neighboring cell. In the LTE standard of therelated art, an eNB can forward a Treselection value to an idle mode UEthrough a SystemInformationBlock3 (SIB3).

TABLE 22 SystemInformationBlockType3 information element -- ASN1STARTSystemInformationsBlockType3 ::= SEQUENCE { cellReselectionInfoCommonSEQUENCE { q-Hyst ENUMERATED { dB0, dB1, dB2, dB3, dB4, dB5, dB6, dB8,dB10, dB12, dB14, dB16, dB18, dB20, dB22, dB24},speedStateReselectionPars SEQUENCE { mobilityStateParametersMobilityStateParameters, q-HystSF SEQUENCE { sf-Medium ENUMERATED {dB-6, dB-4, dB-2, dB0}, sf-High ENUMERATED { dB-6, dB-4, dB-2, dB0} } }OPTIONAL -- Need OP }, cellReselectionServingFreqInfo SEQUENCE {s-NonIntraSearch ReselectionThreshold OPTIONAL, -- Need OPthreshServingLow ReselectionThreshold, cellReselectionPriorityCellReselectionPriority }, intraFreqCellReselectionInfo SEQUENCE {q-RxLevMin Q-RxLevMin, p-Max P-Max OPTIONAL, -- Need OP s-IntraSearchReselectionThreshold OPTIONAL, -- Need OP allowedMeasBandwidthAllowedMeasBandwidth OPTIONAL, -- Need OP presenceAntennaPort1PresenceAntennaPort1, neighCellConfig NeighCellConfig,t-ReselectionEUTRA T-Reselection, cellIndividualInfoListCellIndividualInfoList OPTIONAL, -- Need OP t-ReselectionEUTRA-SFSpeedStateScaleFactors OPTIONAL -- Need OP cellTypeList CellTypeList },... } CellIndividualInfoList ::= SEQUENCE (SIZE (1..N)) OFCellIndividualInfo CellIndividualInfo ::= SEQUENCE { physCellIdPhysCellId, cellIndividual-t-ReselectionEUTRA T-Reselection } --ASN1STOP

In general, the SIB3 includes common information for performing cellreselection irrespective of intra-frequency/inter-frequency/inter-RATcell reselection.

This example (2-1) has no restriction even from any SIB that an idlemode UE can receive but, as an exemplary embodiment, is set to the SIB3currently including the Treselection value.

As in the drawings, an exemplary embodiment of the present inventionnewly proposes a ‘cellIndividualInfoList’ field that is a part shown ina highlighted color in the SIB3. Within the ‘cellIndividualInfoList’field, ‘cellIndividualInfo’ fields of ‘N’ number are set.

Within the ‘cellIndividualInfo’ field, a ‘cellIndividual-t-Reselection’field that is a Treselection value independently every neighboring cellis set. A phyCellId and a cellIndividual-t-ReselectionEUTRA are shown inTable 23 below.

TABLE 23 phyCellId Physical cell identity of a cell in neighboring celllist. cellIndividual-t-ReselectionEUTRA Cell individual parameter“TreselectionEUTRAN” applicable to a specific neighboring cell.

Table 24 relates to a method of applying and setting an SF value setconsidering an existing speed of a UE, to a Treselection-SF valueindependently by a specific neighboring cell according to an exemplaryembodiment of the present invention.

Table 24 relates to a method (2-2) for setting a Treselection-SF valueindependently by a specific neighboring cell. Like the TTT-SF, thecurrent LTE standard applies a ‘speed-dependent’ SF according to a speedof a UE.

TABLE 24 SystemInformationBlockType3 information element -- ASN1STARTSystemInformationBlockType3 ::= SEQUENCE { cellReselectionInfoCommonSEQUENCE { q-Hyst ENUMERATED { dB0, dB1, dB2, dB3, dB4, dB5, dB6, dB8,dB10, dB12, dB14, dB16, dB18, dB20, dB22, dB24},speedStateReselectionPars SEQUENCE { mobilityStateParametersMobilityStateParameters, q-HystSF SEQUENCE { sf-Medium ENUMERATED {dB-6, dB-4, dB-2, dB0}, sf-High ENUMERATED { dB-6, dB-4, dB-2, dB0} } }OPTIONAL -- Need OP }, cellReselectionServingFreqInfo SEQUENCE {s-NonIntraSearch ReselectionThreshold OPTIONAL, -- Need OPthreshServingLow ReselectionThreshold, cellReselectionPriorityCellReselectionPriority }, intraFreqCellReselectionInfo SEQUENCE {q-RxLevMin Q-RxLevMin, p-Max P-Max OPTIONAL, -- Need OP s-IntraSearchReselectionThreshold OPTIONAL, -- Need OP allowedMeasBandwidthAllowedMeasBandwidth OPTIONAL, -- Need OP presenceAntennaPort1PresenceAntennaPort1, neighCellConfig NeighCellConfig,t-ReselectionEUTRA T-Reselection, cellIndividualInfoListCellIndividualInfoList OPTIONAL, -- Need OP t-ReselectionEUTRA-SFSpeedStateScaleFactors OPTIONAL -- Need OP cellTypeList CellTypeList },... } CellIndividualInfoList ::= SEQUENCE (SIZE (1..N)) OFCellIndividualInfo CellIndividualInfo ::= SEQUENCE { physCellIdPhysCellId, cellIndividual-t-ReselectionEUTRA-SF SpeedStateScaleFactors} -- ASN1STOP

In a case where an idle mode UE has high and medium mobility, Table 24applies multiplying a Treselection value by an sf-High value and ansf-Medium value. So, in a case where a UE is fast in speed, Table 24 canapply a Treselection value less than an originally given Treselectionvalue.

The example (2-2) can apply (2-2-1) SF values set considering a speedstate of an idle mode UE presented in the LTE standard, or can newly set(2-2-2) separate SF values.

And, the example (2-2) is irrespective of even any SIB that an idle modeUE can receive but, as an exemplary embodiment, is set to an SIB3currently including a Treselection-SF value.

As in the drawings, an exemplary embodiment of the present inventionnewly proposes a ‘cellIndividualInforList’ field that is a part shown ina highlighted color in the SIB3. Within the ‘cellIndividualInfoList’field, ‘cellIndividualInfo’ fields of ‘N’ number are set.

Within the ‘cellIndividualInfo’ field, a‘cellIndividual-t-Reselection-SF’ field that is a Treselection-SF valueindependently each neighboring cell is set.

The added ‘cellIndividual-t-Reselection-SF’ field means a cellindividual Treselection-SF value applied to a specific neighboring cell.In the case of the specific neighboring cell, Table 24 can multiply anoriginally given Treselection value by the SF value and set a TTT short.

Here, Table 24 applies (2-2-1), as it is, a SpeedStateScaleFactors IEthat includes SF values set considering a speed state of a UE presentedin the LTE standard. Here, a phyCellId and acellIndividual-t-ReselectionEUTRA-SF are shown in Table 25 below.

TABLE 25 phyCellId Physical cell identity of a cell in neighboring celllist. cellIndividual-t-ReselectionEUTRA-SF Cell individual parameter“Speed dependent Scaling Factor for TreselectionEUTRAN”

Table 26 illustrates a case of newly setting separate SF values to aTreselection-SF value independently by a specific neighboring cellaccording to an exemplary embodiment of the present invention.

In the case of newly setting the separate SF values, an exemplaryembodiment of the present invention newly proposes a‘cellIndividualInfoList’ field that is a part shown in a highlightedcolor in an SIB3.

TABLE 26 SystemInformationBlockType3 information element -- ASN1STARTSystemInformationBlockType3 ::= SEQUENCE { cellReselectionInfoCommonSEQUENCE { q-Hyst ENUMERATED { dB0, dB1, dB2, dB3, dB4, dB5, dB6, dB8,dB10, dB12, dB14, dB16, dB18, dB20, dB22, dB24},speedStateReselectionPars SEQUENCE { mobilityStateParametersMobilityStateParameters, q-HystSF SEQUENCE { sf-Medium ENUMERATED {dB-6, dB-4, dB-2, dB0}, sf-High ENUMERATED { dB-6, dB-4, dB-2, dB0} } }OPTIONAL -- Need OP }, cellReselectionServingFreqInfo SEQUENCE {s-NonIntraSearch ReselectionThreshold OPTIONAL, -- Need OPthreshServingLow ReselectionThreshold, cellReselectionPriorityCellReselectionPriority }, intraFreqCellReselectionInfo SEQUENCE {q-RxLevMin Q-RxLevMin, p-Max P-Max OPTIONAL, -- Need OP s-IntraSearchReselectionThreshold OPTIONAL, -- Need OP allowedMeasBandwidthAllowedMeasBandwidth OPTIONAL, -- Need OP presenceAntennaPort1PresenceAntennaPort1, neighCellConfig NeighCellConfig,t-ReselectionEUTRA T-Reselection, cellIndividualInfoListCellIndividualInfoList OPTIONAL, -- Need OP t-ReselectionEUTRA-SFSpeedStateScaleFactors OPTIONAL -- Need OP cellTypeList CellTypeList },... } CellIndividualInfoList ::= SEQUENCE (SIZE (1..N)) OFCellIndividualInfo CellIndividualInfo ::= SEQUENCE { physCellIdPhysCellId, cellIndividual-t-ReselectionEUTRA-SFCellIndividualScaleFactors } -- ASN1STOP

Within the ‘cellIndividualInfoList’ field, ‘cellIndividualInfo’ fieldsof ‘N’ number are set. Within the ‘cellIndividualInfo’ field, a‘cellIndividual-t-Reselection-SF’ field that is a Treselection-SF valueindependently by a neighboring cell is set.

The added ‘cellIndividual-t-Reselection-SF’ field means a cellindividual Treselection-SF value applied to a specific neighboring cell.In the case of the specific neighboring cell, Table 26 can multiply anoriginally given Treselection value by the SF value and set a TTT short.

Here, an exemplary embodiment of the present invention uses (2-2-2)‘CellIndividualScaleFactors’ that are a newly defined scale factorrelated IE. Here, a phyCellId and a cellIndividual-t-ReselectionEUTRA-SFare shown in Table 27 below.

TABLE 27 phyCellId Physical cell identity of a cell in neighboring celllist. cellIndividual-t-ReselectionEUTRA-SF Cell individual parameter“Speed dependent Scaling Factor for TreselectionEUTRAN”CellIndividualScaleFactors information element -- ASN1STARTCellIndividualScaleFactors ::= ENUMERATED (x_1, x_2, . . . , x_n) --ASN1STOP

Here, ‘x_1’, ‘x_2’, . . . , ‘x_n’ values are mapped to values of 0 to 1.

Table 28 illustrates a case of setting a Treselection value by aneighboring cell belonging to a specific cell type according to anexemplary embodiment of the present invention.

Table 28 relates to a method (2-3) for setting a Treselection valueindependently by neighboring cells belonging to the specific cell type.Table 28 has no restriction from any SIB that an idle mode UE canreceive but, as an exemplary embodiment, is set to an SIB3 currentlyincluding the Treselection value.

TABLE 28 SystemInformationBlockType3 information element -- ASN1STARTSystemInformationBlockType3 ::= SEQUENCE { cellReselectionInfoCommonSEQUENCE { q-Hyst ENUMERATED { dB0, dB1, dB2, dB3, dB4, dB5, dB6, dB8,dB10, dB12, dB14, dB16, dB18, dB20, dB22, dB24},speedStateReselectionPars SEQUENCE { mobilityStateParametersMobilityStateParameters, q-HystSF SEQUENCE { sf-Medium ENUMERATED {dB-6, dB-4, dB-2, dB0}, sf-High ENUMERATED { dB-6, dB-4, dB-2, dB0} } }OPTIONAL -- Need OP }, cellReselectionServingFreqInfo SEQUENCE {s-NonIntraSearch ReselectionThreshold OPTIONAL, -- Need OPthreshServingLow ReselectionThreshold, cellReselectionPriorityCellReselectionPriority }, intraFreqCellReselectionInfo SEQUENCE {q-RxLevMin Q-RxLevMin, p-Max P-Max OPTIONAL, -- Need OP s-IntraSearchReselectionThreshold OPTIONAL, -- Need OP allowedMeasBandwidthAllowedMeasBandwidth OPTIONAL, -- Need OP presenceAntennaPort1PresenceAntennaPort1, neighCellConfig NeighCellConfig,t-ReselectionEUTRA T-Reselection, cellIndividualInfoListCellIndividualInfoList OPTIONAL, -- Need OP t-ReselectionEUTRA-SFSpeedStateScaleFactors OPTIONAL -- Need OP cellTypeList CellTypeList },... } CellIndividualInfoList ::= SEQUENCE (SIZE (1..N)) OFCellIndividualInfo CellIndividualInfo ::= SEQUENCE { physCellRangePhysCellRange, cellIndividual-t-ReselectionEUTRA T-Reselection } --ASN1STOP

In Table 28, an exemplary embodiment of the present invention newlyproposes a ‘cellIndividualInfoList’ field that is a part shown in ahighlighted color in the SIB3. Within the ‘cellIndividualInfoList’field, ‘cellIndividualInfo’ fields of ‘N’ number are set.

Within the ‘cellIndividualInfo’ field, a‘cellIndividual-t-ReselectionEUTRA’ field that is a Treselection valueindependently every PCI range of a specific cell type is set. AphyCellIdRange and a cellIndividual-t-ReselectionEUTRA are shown inTable 29 below.

TABLE 29 phyCellIdRange A range of physical cell identities inneighboring cell list. cellIndividual-t-ReselectionEUTRA Cell individualparameter “TreselectionEUTRAN” applicable to a specific neighboring cell

Table 30 relates to a method of applying SF values set considering anexisting speed of a UE and setting a Treselection-SF value byneighboring cell belonging to a specific cell type according to anexemplary embodiment of the present invention.

Table 30 relates to a method (2-4) for setting a Treselection-SF valueindependently by neighboring cells belonging to a specific cell type.Table 30 is irrespective of any SIB that an idle mode UE can receivebut, as an exemplary embodiment, is set to an SIB3 currently includingthe Treselection-SF value. The example (2-4) can consider an example(2-4-1) for applying and setting SF values set considering an existingspeed state of a UE.

TABLE 30 SystemInformationBlockType3 information element -- ASN1STARTSystemInformationsBlockType3 ::= SEQUENCE { cellReselectionInfoCommonSEQUENCE { q-Hyst ENUMERATED { dB0, dB1, dB2, dB3, dB4, dB5, dB6, dB8,dB10, dB12, dB14, dB16, dB18, dB20, dB22, dB24},speedStateReselectionPars SEQUENCE { mobilityStateParametersMobilityStateParameters, q-HystSF SEQUENCE { sf-Medium ENUMERATED {dB-6, dB-4, dB-2, dB0}, sf-High ENUMERATED { dB-6, dB-4, dB-2, dB0} } }OPTIONAL -- Need OP }, cellReselectionServingFreqInfo SEQUENCE {s-NonIntraSearch ReselectionThreshold OPTIONAL, -- Need OPthreshServingLow ReselectionThreshold, cellReselectionPriorityCellReselectionPriority }, intraFreqCellReselectionInfo SEQUENCE {q-RxLevMin Q-RxLevMin, p-Max P-Max OPTIONAL, -- Need OP s-IntraSearchReselectionThreshold OPTIONAL, -- Need OP allowedMeasBandwidthAllowedMeasBandwidth OPTIONAL, -- Need OP presenceAntennaPort1PresenceAntennaPort1, neighCellConfig NeighCellConfig,t-ReselectionEUTRA T-Reselection, cellIndividualInfoListCellIndividualInfoList OPTIONAL, -- Need OP t-ReselectionEUTRA-SFSpeedStateScaleFactors OPTIONAL -- Need OP cellTypeList CellTypeList },... } CellIndividualInfoList ::= SEQUENCE (SIZE (1..N)) OFCellIndividualInfo CellIndividualInfo ::= SEQUENCE { physCellRangePhysCellRange, cellIndividual-t-ReselectionEUTRA-SFSpeedStateScaleFactors } -- ASN1STOP

As in Table 30, an exemplary embodiment of the present invention newlyproposes a ‘cellIndividualInfoList’ field that is a part shown in ahighlighted color in an SIB3. Within the ‘cellIndividualInfoList’ field,‘cellIndividualInfo’ fields of ‘N’ number are set.

Within the ‘cellIndividualInfo’ field, a‘cellIndividual-t-ReselectionEUTRA’ field that is a Treselection valueindependently every PCI range of a specific cell type is set.

The added ‘cellIndividual-t-Reselection-SF’ field means a cellindividual Treselection-SF value applied to a specific neighboring cell.In the case of the specific neighboring cell, Table 30 can multiply anoriginally given Treselection value by the SF value and set a TTT short.

Here, Table 30 applies a SpeedStateScaleFactors IE that is an SF valueset considering a speed state of a UE presented in the LTE standard ofthe related art as it is. Here, a phyCellIdRange and acellIndividual-t-ReselectionEUTRA-SF are shown in Table 31 below.

TABLE 31 PhyCellIdRange A range of physical cell identities inneighboring cell list. cellIndividual-t-ReselectionEUTRA-SF Cellindividual parameter “Speed dependent Scaling Factor forTreselectionEUTRAN”

Table 32 relates to a method of newly setting, in consideration of anexisting speed of a UE, a Treselection-SF value by a neighboring cellbelonging to a specific cell type according to an exemplary embodimentof the present invention.

Table 31 relates to a method (2-4) for setting a Treselection-SF valueindependently by neighboring cells belonging to a specific cell type.Table 31 is irrespective of any SIB that an idle mode UE can receivebut, as an exemplary embodiment, is set to an SIB3 currently includingthe Treselection-SF value. The example (2-4) can consider an example(2-4-2) for newly setting separate SF values considering an existingspeed state of a UE.

TABLE 32 SystemInformationBlockType3 information element -- ASN1STARTSystemInformationBlockType3 ::= SEQUENCE { cellReselectionInfoCommonSEQUENCE { q-Hyst ENUMERATED { dB0, dB1, dB2, dB3, dB4, dB5, dB6, dB8,dB10, dB12, dB14, dB16, dB18, dB20, dB22, dB24},speedStateReselectionPars SEQUENCE { mobilityStateParametersMobilityStateParameters, q-HystSF SEQUENCE { sf-Medium ENUMERATED {dB-6, dB-4, dB-2, dB0}, sf-High ENUMERATED { dB-6, dB-4, dB-2, dB0} } }OPTIONAL -- Need OP }, cellReselectionServingFreqInfo SEQUENCE {s-NonIntraSearch ReselectionThreshold OPTIONAL, -- Need OPthreshServingLow ReselectionThreshold, cellReselectionPriorityCellReselectionPriority }, intraFreqCellReselectionInfo SEQUENCE {q-RxLevMin Q-RxLevMin, p-Max P-Max OPTIONAL, -- Need OP s-IntraSearchReselectionThreshold OPTIONAL, -- Need OP allowedMeasBandwidthAllowedMeasBandwidth OPTIONAL, -- Need OP presenceAntennaPort1PresenceAntennaPort1, neighCellConfig NeighCellConfig,t-ReselectionEUTRA T-Reselection, cellIndividualInfoListCellIndividualInfoList OPTIONAL, -- Need OP t-ReselectionEUTRA-SFSpeedStateScaleFactors OPTIONAL -- Need OP cellTypeList CellTypeList },... } CellIndividualInfoList ::= SEQUENCE (SIZE (1..N)) OFCellIndividualInfo CellIndividualInfo ::= SEQUENCE { physCellRangePhysCellRange, cellIndividual-t-ReselectionEUTRA-SFCellIndividualScaleFactors } -- ASN1STOP

As in Table 32, an exemplary embodiment of the present invention newlyproposes a ‘cellIndividualInfoList’ field that is a part shown in ahighlighted color in an SIB3.

Within the ‘cellIndividualInfoList’ field, ‘cellIndividualInfo’ fieldsof ‘N’ number are set. Within the ‘cellIndividualInfo’ field, a‘cellIndividual-t-ReselectionEUTRA’ field that is a Treselection valueindependently every PCI range of a specific cell type is set.

The added ‘cellIndividual-t-Reselection-SF’ field means a cellindividual Treselection-SF value applied to a specific neighboring cell.In the case of the specific neighboring cell, Table 32 can multiply anoriginally given Treselection value by the SF value and set a TTT short.

Here, Table 32 applies ‘SpeedStateScaleFactors’ that include a newlydefined scale factor related IE. Here, a phyCellId and acellIndividual-t-ReselectionEUTRA-SF are shown in Table 33 below.

TABLE 33 phyCellId Physical cell identity of a cell in neighboring celllist. cellIndividual-t-ReselectionEUTRA-SF Cell individual parameter“Speed dependent Scaling Factor for TreselectionEUTRAN”CellIndividualScaleFactors information element -- ASN1STARTCellIndividualScaleFactors ::= ENUMERATED (x_1, x_2, . . . , x_n) --ASN1STOP

Here, ‘x_1’, ‘x_2’, . . . , ‘x_n’ values are mapped to values of 0 to 1.

FIG. 11 is a block diagram illustrating a construction of an eNB or a UEaccording to an exemplary embodiment of the present invention.

Referring to FIG. 11, the eNB (or the UE) includes a duplexer 1100, aRadio Frequency (RF) receiver 1102, an Analog to Digital Converter (ADC)1104, an Orthogonal Frequency Division Multiplexing (OFDM) demodulator1106, a decoder 1108, a message processor 1110, a controller 1112, amessage generator 1114, an encoder 1116, an OFDM modulator 1118, aDigital to Analog Converter (DAC) 1120, and an RF transmitter 1122.

According to a duplexing scheme, the duplexer 1100 forwards, to the RFreceiver 1102, a received signal from an antenna, and transmits atransmit signal from the RF transmitter 1122 through the antenna.

The RF receiver 1102 converts an RF signal from the duplexer 1100 into abaseband analog signal. The ADC 1104 converts the analog signal from theRF receiver 1102 into sample data. The OFDM demodulator 1106 processes,by Fast Fourier Transform (FFT), the sample data output from the ADC1104, and outputs frequency domain data.

The decoder 1108 selects data (i.e., burst data) of subcarriers, whichis intended for reception, among the frequency domain data from the OFDMdemodulator 1106, and processes, by demodulation and decoding, theselected data according to a predefined modulation level (i.e., aModulation and Coding Scheme (MCS) level).

The message processor 1110 detects a packet (e.g., a Media AccessControl Protocol Data Unit (MAC PDU)) of a predetermined unit in thedata from the decoder 1108, and performs a header and error check forthe detected packet. At this time, if it is determined to be a controlmessage through the header check, the message processor 1110 interpretsthe control message according to a defined standard, and provides theresult to the controller 1112. That is, the message processor 1110extracts various kinds of control information from the received controlmessage and forwards the extracted control information to the controller1112.

The controller 1112 performs corresponding processing based on theinformation from the message processor 1110. Also, when there is a needto transmit a control message, the controller 1112 generatescorresponding information and provides the generated information to themessage generator 1114. The message generator 1114 generates a messageby means of various kinds of the information provided from thecontroller 1112 and outputs the generated message to the encoder 1116 ofa physical layer.

The encoder 1116 encodes and modulates data from the message generator1114, according to a predefined modulation level (i.e., an MCS level).The OFDM modulator 1118 processes, by Inverse Fast Fourier Transform(IFFT), the data from the encoder 1116 and outputs sample data (i.e.,OFDM symbols). The DAC 1120 converts the sample data into an analogsignal. The RF transmitter 1122 converts the analog signal from the DAC1120 into an RF signal and transmits the RF signal through the antenna.

In the aforementioned construction, the controller 1112, a protocolcontroller, controls the message processor 1110 and the messagegenerator 1114. That is, the controller 1112 can perform functions ofthe message processor 1110 and the message generator 1114. These areseparately constructed and shown in order to distinguish and describerespective functions in an exemplary embodiment of the presentinvention. Thus, in an actual realization, construction can be such thatall the functions are processed in the controller 1112, or constructioncan be such that only part of the functions is processed in thecontroller 1112.

Next, operations of the eNB and the UE are described, respectively,based on the construction of FIG. 11.

Regarding a description of the eNB, the controller 1112 generates itsown TTT and handover trigger threshold values independently by aneighboring eNB or reads out the TTT and handover trigger thresholdvalues from a storage unit (not shown), and provides the TTT andhandover trigger threshold values to the message generator 1114. Themessage generator 1114 generates a corresponding message and outputs thegenerated message to the encoder 1116. The controller 1112 performscorresponding processing when receiving a control message (i.e., an IE)of an exemplary embodiment of the present invention from the messageprocessor 1110.

Or, the controller 1112 generates information such as a TTT, a TTT-SF, aTreselection, a Treselection-SF and the like that are information of anexemplary embodiment of the present invention to be transmitted to a UEor reads out the information from the storage unit (not shown), andprovides the information to the message generator 1114. The messagegenerator 1114 generates a corresponding message and outputs the messageto the encoder 1116.

Regarding a description of the UE, when receiving information such as aTTT, a TTT-SF, a Treselection, a Treselection-SF and the like from themessage processor 1110, the controller 1112 enables operation byapplying the information when the UE performs handover or cellreselection.

Henceforth, an analysis of the performance of an exemplary embodiment ofthe present invention is described below. A hot zone cell describedherein is the same as a micro cell.

FIG. 12 is a graph illustrating the result of an HO fail ratio when aload factor is 50% and a UL Interoperability Test (IoT) is 5 dBaccording to an exemplary embodiment of the present invention, and FIG.13 is a graph illustrating the result of an HO fail ratio when the loadfactor is 100% and the UL IoT is 7 dB according to an exemplaryembodiment of the present invention.

Referring to FIG. 12, an HO fail ratio acceptable on system managementdefinition is equal to 2%, so it can be appreciated from the aboveperformance graph that the optimum set parameters are TTT=80 to 160 msand Cell Individual Offset (CIO)=1 to 3 dB in a DL 50% load environmentfrom a macro cell to a macro cell, while the optimum set parameters areTTT=0 to 80 ms and CIO=1 to 3 dB in an environment from a macro cell toa micro cell.

Referring to FIG. 13, it can also be appreciated that the optimum setparameters are TTT=40 ms and CIO=1 dB in a 100% load environment from amacro cell to a macro cell, while the optimum set parameters are TTT=0ms and CIO=1 dB to 3 dB in an environment from a macro cell to a microcell.

As described above, exemplary embodiments of the present invention havean advantage of being capable of improving an HO performance successratio between a macro cell and a micro cell because negotiating TTTrelated information between macro and micro eNBs supports a stable HOsuccess when a UE performs handover between the macro cell and the microcell.

Also, the exemplary embodiments of the present invention have anadvantage in that a serving eNB can forward a TTT value independently bya specific neighboring eNB to an active mode UE for the sake ofperforming stable handover between a macro cell and a micro cell in anLTE system.

Also, the exemplary embodiments of the present invention propose a wayfor an eNB to forward a Treselection value independently by aneighboring cell belonging to a specific cell type, to an idle mode UEfor the sake of stable cell reselection performance between a macro celland a micro cell in an LTE system, thereby advantageously improving anHO performance success ratio between the macro cell and the micro cell.

While the invention has been shown and described with reference tocertain exemplary embodiments thereof, it will be understood by thoseskilled in the art that various changes in form and details may be madetherein without departing from the spirit and scope of the invention asdefined by the appended claims and their equivalents.

What is claimed is:
 1. A method for operating a mobile station in amobile communication system, the method comprising: receiving, from aserving cell, a message including first information indicating a time totrigger (TTT) for at least one first neighbor cell and an alternativeTTT for at least one second neighbor cell, and second informationindicating at least one list of the at least one second neighbor cell,wherein the TTT and the alternative TTT are included in separate fieldsof the message; identifying the TTT and the alternative TTT included inthe message; and transmitting, to the serving cell, a measurement reportfor the at least one second neighbor cell based on the alternative TTT,wherein the alternative TTT is used for the at least one second neighborcell instead of the TTT, and wherein the second information includes aphysical cell identifier range indicating a range of physical cellidentities in the at least one list.
 2. The method of claim 1, whereinthe second information is included in MeasObjectEUTRA informationelement (IE).
 3. The method of claim 1, wherein the alternative TTT isincluded in ReportConfigEUTRA information element (IE).
 4. A mobilestation in a mobile communication system, the mobile station comprising:a transceiver; and at least one processor, wherein the at least oneprocessor is configured to: control the transceiver to receive, from aserving cell, a message including first information indicating a time totrigger (TTT) for at least one first neighbor cell and an alternativeTTT for at least one second neighbor cell, and second informationindicating at least one list of the at least one second neighbor cell,wherein the TTT and the alternative TTT are included in separate fieldsof the message, identify the TTT and the alternative TTT included in themessage, and control the transceiver to transmit, to the serving cell, ameasurement report for the at least one second neighbor cell based onthe alternative TTT instead of the first TTT, wherein the alternativeTTT is used for the at least one second neighbor cell instead of theTTT, and wherein the second information includes a physical cellidentifier range indicating a range of physical cell identities in theat least one list.
 5. The mobile station of claim 4, wherein the secondinformation is included in MeasObjectEUTRA information element (IE). 6.The mobile station of claim 4, wherein the alternative TTT is includedin ReportConfigEUTRA information element (IE).